#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<assert.h>
#include<stdbool.h>
#include<stdlib.h>

typedef int STDataType;
typedef struct Stack
{
	STDataType* a;
	int top;
	int capacity;
}ST;

void STInit(ST* ps)
{
	assert(ps);

	ps->a = NULL;
	ps->top = ps->capacity = 0;
}
void STDestroy(ST* ps)
{
	assert(ps);
	free(ps->a);
	ps->a = NULL;
	ps->top = ps->capacity = 0;
}

void STPush(ST* ps, STDataType x)
{
	assert(ps);

	if (ps->top == ps->capacity)
	{
		int newcapacity = ps->capacity == 0 ? 4: 2 * ps->capacity;
		STDataType* tmp = (STDataType*)realloc(ps->a, sizeof(STDataType) * newcapacity);
		if (tmp == NULL)
		{
			perror("realloc fail!");
			return;
		}
		ps->a = tmp;
		ps->capacity = newcapacity;
	}
	ps->a[ps->top] = x;
	ps->top++;
}

bool STEmpty(ST* ps)
{
	assert(ps);

	return ps->top == 0;
}
void STPop(ST* ps)
{
	assert(ps);
	assert(!STEmpty(ps));

	ps->top--;
}
STDataType STTop(ST* ps)
{
	assert(ps);
	assert(!STEmpty(ps));

	return ps->a[ps->top - 1];
}
int STSize(ST* ps)
{
	assert(ps);
	return ps->top;
}

//int main()
//{
//	ST s;
//	STInit(&s);
//
//	STPush(&s, 1);
//	STPush(&s, 2);
//	STPush(&s, 3);
//	STPush(&s, 4);
//	while (!STEmpty(&s))
//	{
//		printf("%d\n", STTop(&s));
//		STPop(&s);
//	}
//	STDestroy(&s);
//
//	return 0;
//}